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-- WITH PHOTO -- TO NATIONAL, SCIENCE, AND TECHNOLOGY EDITORS:
High-Performance, Low-Cost Ultracapacitors Built with Graphene and
Carbon Nanotubes
WASHINGTON, April 22, 2014 /PRNewswire-USNewswire/ -- By combining the
powers of two single-atom-thick carbon structures, researchers at the
George Washington University's Micro-propulsion and Nanotechnology
Laboratory have created a new ultracapacitor that is both high
performance and low cost.
The device, described in the Journal of Applied Physics, capitalizes
on the synergy brought by mixing graphene flakes with single-walled
carbon nanotubes, two carbon nanostructures with complementary
properties.
Ultracapacitors are souped-up energy storage devices that hold high
amounts of energy and can also quickly release that energy in a surge
of power. By combining the high energy-density properties of batteries
with the high power-density properties of conventional capacitors,
ultracapacitors can boost the performance of electric vehicles,
handheld electronics, audio systems and more.
Single-walled carbon nanotubes and graphene both have unique and
excellent electronic, thermal, and mechanical properties that make
them attractive materials for designing new ultracapacitors, said Jian
Li, first author on the paper. Many groups had explored the use of the
two materials separately, but few had looked at combining them, he
said.
"In our lab we developed an approach by which we can obtain both
single-walled carbon nanotubes and graphene, so we came up with the
idea to take advantage of the two promising carbon nanomaterials
together," added Michael Keidar, a professor in the Department of
Mechanical and Aerospace Engineering in the School of Engineering and
Applied Science at GW, and director of the Micro-propulsion and
Nanotechnology Laboratory.
The researchers synthesized the graphene flakes and nanotubes by
vaporizing a hollow graphite rod filled with metallic catalyst powder
with an electric arc. They then mixed the two nanostructures together
to form an ink that they rolled onto paper, a common separator for
current commercial capacitors.
The combination device's specific capacitance, a measurement of the
performance of a capacitor per unit of weight, was three times higher
than the specific capacitance of a device made from carbon nanotubes
alone.
The advantage of the hybrid structure, Li explained, is that the
graphene flakes provide high surface area and good in-plane
conductivity, while the carbon nanotubes connect all of the structures
to form a uniform network.
While other types of ultracapacitors have also achieved the high
specific capacitance of the graphene/nanotube hybrid, the researchers
say, the main advantage of the combination approach is its low costs,
since the team has developed a simple way to manufacture large amounts
of the desirable mix of carbon nanostructures.
The hybrid ultracapacitor is also small and light, an advantage as
electronic devices get ever smaller.
MORE INFORMATION: The George Washington University's Micro-propulsion
and Nanotechnology Laboratory: https://www.mpnl.seas.gwu.edu
The article, "Paper-based ultracapacitors with carbon
nanotubes-graphene composites" is authored by Jian Li, Xiaoqian Cheng,
Jianwei Sun, Cameron Brand, Alexey Shashurin, Mark Reeves and Michael
Keidar. It will be published in the Journal of Applied Physics on
April 22, 2014 (DOI: 10.1063/1.4871290). After that date, it can be
accessed at:
http://scitation.aip.org/content/aip/journal/jap/115/16/10.1063/1.4871290
This work was supported by the NSF/DOE Partnership in Plasma Science
and Technology (NSF Grant No. CBET-0853777 and DOE Grant No.
DE-SC0001169), and an NSF Award (Title: EAGER: Exploring plasma
mechanism of synthesis of graphene in arc discharge, NSF Award No.
1249213).
ABOUT THE JOURNAL Journal of Applied Physics, published by the
American Institute of Physics, is an influential international journal
publishing significant new experimental and theoretical results of
applied physics research. See: http://jap.aip.org
More Information: Jason Socrates Bardi +1 240-535-4954 jbardi@aip.org
@jasonbardi
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SOURCE Journal of Applied Physics
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